Authenticated privilege escalation via Negotiate parsing
Published Jul 14, 2026 · Updated Jul 14, 2026
Improper parsing in ASP.NET Core Negotiate Authentication in .NET 8, 9, and 10 allows remote authenticated users to elevate privileges. The Negotiate authentication handler parses attacker-controlled authentication data incorrectly; Microsoft has not disclosed the malformed element or resulting authorization decision. Exposure requires an application using a vulnerable Microsoft.AspNetCore.Authentication.Negotiate package, and successful exploitation grants privileges beyond the authenticated account.
Summary
What happened
Improper parsing in ASP.NET Core Negotiate Authentication in .NET 8, 9, and 10 allows remote authenticated users to elevate privileges. The Negotiate authentication handler parses attacker-controlled authentication data incorrectly; Microsoft has not disclosed the malformed element or resulting authorization decision. Exposure requires an application using a vulnerable Microsoft.AspNetCore.Authentication.Negotiate package, and successful exploitation grants privileges beyond the authenticated account.
The record
- CVE
- CVE-2026-47303
- Published
- Jul 14, 2026
- Updated
- Jul 14, 2026
- Vendor
- Microsoft
- Product
- .NET 9.0
- Classifications
- CWE-863, CWE-90, CWE-302, T1068
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 14, 2026CVE publishedPublication date reported by the CVE source.
- Jul 14, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=9.0.0 <9.0.18
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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